From practice automatic or automated transmissions having a pneumatically or hydraulically actuated automated clutch, in particular a pneumatically or hydraulically actuated starting clutch are known, wherein the clutch of the transmission is actuated to open and to close by a pneumatic or hydraulic clutch actuator. Such a clutch actuator has an actuating cylinder which is coupled to the clutch, with control valves associated with the actuating cylinder of the clutch actuator, and depending on their switched position these valves either fill or empty the actuating cylinder. The control valves of the clutch actuator are controlled by a control unit.
A clutch arranged in the drive-train of a motor vehicle, between a drive motor, for example in the form of an internal combustion engine, and a manual transmission, serves during traction operation to transmit torque from the drive motor to the manual transmission; during overdrive operation it also acts in the reverse direction. In its non-activated condition the clutch is fully closed by the action of a pressure spring, and transmits the torque without slip by virtue of static friction. In starting processes, shifting processes and emergency braking the clutch is opened and the power flow between the drive motor and the manual transmission is therefore temporarily interrupted or at least reduced.
In a starting process, when a starting gear has been engaged the clutch is closed again continuously, whereby the torque of the drive motor is transmitted in slipping operation by sliding friction, and thereby a rotational speed equalization takes place between the drive output shaft of the rapidly rotating drive motor and the initially static and then at first more slowly rotating input shaft of the manual transmission. In a shifting process between an engaged, loaded gear and a target gear to be engaged, opening of the clutch enables the loaded gear to be disengaged while free from load and thereafter enables the load-free synchronization and engagement of the target gear. During emergency braking, opening the clutch allows the drive force of the drive motor to be taken up by the drive wheels.
It is very important that the clutch actuator that serves to actuate the clutch should operate in a leakproof manner. Thus, leakproofness of the clutch actuator is vital for the correct operation of the clutch or its clutch actuator. Typically an operating temperature range is defined, within which the clutch actuator must have a specified leakproofness, whereas outside this defined operating temperature range operation of the clutch actuator and hence operation of the clutch are not permitted.
From DE 10 2009 045 090 A1 a method for operating an automated clutch is known. During the operation of the transmission, if defined operating conditions occur, such as the temperature falling below a limiting temperature value, the leakproofness of a clutch actuator serving to operate the clutch is checked. On the basis of that check, it can then be decided whether, and if needs be under which conditions further operation of the clutch is permissible.